1. Industrial Field of the Invention
The present invention relates to a fuel outflow preventing apparatus of a fuel tank for a vehicle.
2. Description of the Prior Art
A conventional evaporated fuel outflow preventing apparatus of a fuel tank for a vehicle is disclosed in Japanese Patent Unexamined Publication No. 61-291218.
In this apparatus, as shown in FIG. 8, the vent tube 4 projectingly provided inside of the tank 1 is connected to the canister 6, so that it communicates with the atmosphere through the canister 6. The float valve 10, which is closed to shut off the vent tube 4 when the fuel in the tank 1 reaches the predetermined level, is installed in the projecting end portion of the vent tube 4 in the tank 1.
As a measure for preventing outflow of evaporated fuel from a filling port 2a of a filler tube 2 at the time of fuel feeding, the periphery of that portion of the filling port 2a where a fuel feeding tank is inserted is sealed with a sealing member (not shown). In such a case, since the vent tube 4 communicates with the atmosphere through the canister 6, an adequate venting function can be obtained from the vent tube 4 so as to carry out fuel feeding smoothly.
During the fuel feeding, the evaporated fuel accumulated in an upper air chamber 8 of the tank 1 is discharged to an evaporation tube 3. In addition, it is discharged through an opening at the bottom of a large-diameter portion 4a of the vent tube 4 and supplied to the canister 6 from the vent tube 4 as well. The evaporated fuel absorbed by either of the canisters 5 and 6 is supplied, with the purge air, to an engine intake system (not shown) where it is processed.
When fuel in the tank 1 reaches a predetermined level, the float valve 10 is closed to prevent the fuel exceeding a predetermined amount from flowing into the tank. Even if the fuel is fed to a level close to a neck portion of the filler tube 2 after preventing the fuel exceeding this predetermined amount flowing in, the fuel will not enter the vent tube 4 because the projecting end portion of the vent tube 4 in the tank 1 is closed by the float valve 10, as described above. Thereafter, the evaporated fuel generated in the upper air chamber 8 of the tank 1 is discharged to the canister 5 via the evaporation tube 3 while the vent tube 4 is closed by the float valve 10. When the fuel level is lowered and the float valve 10 is opened, however, the evaporated fuel is also discharged to the canister 6 via the vent tube 4 and processed in the above-mentioned manner.
In the conventional technique described above, when the vehicle is inclined at a predetermined angle or more, or when it is turned over, the fuel in the tank will flow out to the canisters, to thereby deteriorate absorbents in the canisters. Further, the fuel will leak out of the vehicle through the canisters, so that it will pollute the atmosphere, and that it is dangerous.
Recently, in some regions, the pressure in the upper air chamber of the tank during traveling of the vehicle is restricted to a predetermined value or less. It is necessary to clear this restriction and to restrict the full amount (the full-tank amount) of the fuel by preventing excessive fuel feeding. In the conventional technique, however, it is questionable whether these two necessities are satisfied.